Fix/nested within dt

[Zegnat]

Fixes #278.

Checklist

• Added tests covering the parsing behaviour changes.
• Linked to any relevant issues this will close.
• Tested the output using the demo.

Changes to parsing behaviour

It will now return nested microformats within dt-* properties. The step “parse a child element for microformats (recurse) ” should always happen for all. And then:

if that child element itself has a microformat ("h-*" or backcompat roots) and is a property element, add it into the array of values for that property

The only thing not specifically designed for dt- is whether we can imply any value. So instead we set value to “the parsed property value per p-*,u-*,dt-* parsing”.

Example input covered by new behaviour

<div class="h-card">
  <div class="dt-bday h-event">
    <time class="dt-start dt-end" datetime="2010-05-02">2nd May</time>
  </div>
</div>

Example output from new behaviour

{
  "rels": {},
  "rel-urls": {},
  "items": [
    {
      "type": [
        "h-card"
      ],
      "properties": {
        "bday": [
          {
            "type": [
              "h-event"
            ],
            "properties": {
              "start": [
                "2010-05-02"
              ],
              "end": [
                "2010-05-02"
              ],
              "name": [
                "2nd May"
              ]
            },
            "value": "2nd May"
          }
        ]
      }
    }
  ]
}

[aimee-gm]

@Zegnat thank you so much for taking the time to make this change!

Also: sorry for respinding earlier!